An engine system may include a main intake line, a supplementary intake line branched from the main intake line and joined to the main intake line, an intake bypass valve mounted to the main intake line, a main exhaust line mounted to an exhaust manifold, a supplementary exhaust line branched from the exhaust manifold and joined to the main exhaust line, an exhaust bypass valve mounted to the main exhaust line and selectively opening the main exhaust line, a turbocharger disposed adjacent to the supplementary exhaust line and operated by exhaust gas passing through the supplementary exhaust line, and a control unit for controlling the intake bypass valve and the exhaust bypass valve depending on an operation condition, wherein the exhaust gas is re-circulated from an upstream side of the exhaust bypass valve to the main intake line passing through an EGR (Exhaust Gas Recirculation) cooler and an EGR valve.